Vitamin D

Step out into the sunshine and you'll get more than just a tan. When the ultraviolet B rays from the sun contact your skin, they activate a series of reactions that produce a hormone called 1,25 dihydroxyvitamin D₃, commonly known as vitamin D. In addition to sunlight, vitamin D is found naturally in some food sources such as egg yolks, herring, and cod liver oil, and is added to other foods such as milk.